This application claims priority under 35 U.S.C. xc2xa7xc2xa7119 and/or 365 to patent application(s) Ser. No. 100 12 821.1 and Ser. No. 100 42 779.0 filed in Germany on Mar. 16, 2000 and Aug. 31, 2000, respectively.
The present invention relates to a cutting-bit bolder for turning tools, i.e., a cutting-bit holder for a turning machine. By xe2x80x9cturningxe2x80x9d is meant machining with a closed generally circular cutting movement by rotating the tool or the workpiece. Chipping takes place during a relative rectilinear feed movement between the workpiece and the tool in a direction perpendicular or parallel to the axis of rotation. By xe2x80x9caxis of rotationxe2x80x9d is meant the axis of rotation of the workpiece when the workpiece turns. If the workpiece is stationary and the tool rotates, e.g., in band-turning machines, facing tools and boring tools with boring bars on boring and milling machines, then the axis of rotation must be understood to be the axis of rotation of the rotating tool.
Such cutting-bit holders are available on the market in many versions. In general, a turning bit (or insert) such as a cutting or cutting-off bit is inserted into and screwed to the cutting-bit holder. The cutting-bit bolder can then be connected to the turning machine. To carry out the cutoff process, the cutting-bit holder is then moved by the turning machine, for example toward the axis of the turning workpiece, so that the cutting insert fixed in the cutting bit holder engages with the workpiece and the latter for example is stripped or cut off.
However, the known cutting-bit holders have the disadvantage that, on the one hand, replacing the turning bit is very time-consuming and, on the other hand in particular when a plurality of grooves is to be incorporated into the workpiece or a plurality of disks is to be cut off from the workpiece, the cut-off process is very time-consuming. That is because the cutting-bit holder, together with the bit, must be moved individually in the direction of feed for each groove or each cut-off process. Moreover, in the case of these versions of holders, the cutting bit is held securely in the cutting-bit holder only after the adjustment of the cutting bit such that, in particular in the case of an overhead mounting, the cutting bit can slip or fall out of the bit holder.
The object of the present invention therefore is to provide a turning assembly, a turning bit, a bit holder, and a turning method for overcoming the above-named disadvantages.
According to the invention, this object is achieved in that the cutting-bit holder is provided for the holding of at least two turning bits (inserts). The turning bits are preferably arranged in the held position such that during the turning process, at least two turning bits can engage simultaneously with the workpiece. Because the cutting-bit holder can hold several turning bits and move them simultaneously in the direction of feed, the turning process can be clearly shortened. Thus, the invention also pertains to an improved turning method.
The turning bits are preferably held in the cutting-bit holder such that they stand essentially parallel to each other.
The cutting-bit holder is particularly preferably developed such that it has at least two holding elements which are each provided for the holding of a turning bit. Because each bit is held by its own holding element, replacement thereof is simplified.
A particularly preferred version provides that the holding elements are adjustable independently of each other in at least one direction, preferably in the direction of feed. Through this feature, the individual bits can be set independently of each other in the direction of feed. It is thereby possible for example to turn grooves of different depths into the work-piece simultaneously with the help of the cutting-bit holder. The bits which are to produce deeper grooves are easily advanced somewhat in the direction of feed together with their holding element vis-xc3xa1-vis the other bits.
The cutting-bit holder expediently has a base body in which the holding elements are arranged, the holding elements being able to be fixed in the base body.
A particularly preferred version provides that a clamping device is arranged for the fixing of the holding elements in the base body. Through the fixing by means of the clamping device, the individual bit can be very quickly housed and fixed in the holding element. It is thereby guaranteed that the individual holding elements, after adjustment in the direction of feed, can be fixed easily and quickly. The holding elements are particularly preferably clamped by the clamping device in a direction which lies perpendicular to the direction of feed, preferably parallel to the axis of rotation.
Particularly expedient is a version of the cutting-bit holder in which the holding elements are able to be replaced. It is thereby possible to either replace the holding elements together with the bit, in order for example to have another bit available without delay, or simply to change a holding element and to mount the bit on the replaced holding element. This may for example be necessary when the clear distance between the different bits is to be changed, as a holding element with another width can then be advantageous.
The holding elements are preferably developed such that the cutting bits can be inserted into the holding element from the direction of feed.
Particularly preferred is a version in which the cutting-bit holder is provided for the heading of the bits in axial direction or longitudinal direction in at least two positions. By xe2x80x9clongitudinalxe2x80x9d direction is meant a direction parallel to the workpiece axis. Through this measure, the distance between two adjacent bits in the cutting-bit holder can be varied. Particularly preferred is a version in which the bits can be varied essentially continuously in the axial direction such that they can be securely fixed or held in almost every position. (It is understood that such a variability cannot be realized with a screw connection of the bit to the holding element or the cutting-bit holder.) A preferred version therefore provides for a clamping device for the fixing of the bits in the axial direction. With the help of this clamping device, this position can be fixed simply and above all quickly after the bits have been adjusted, i.e. have been positioned correctly both in the direction of feed and in the axial direction.
An expedient version provides that at least one spacer is provided for insertion between adjacent bits. In particular when not every bit is to be individually fixed or clamped to the holding element or in the cutting-bit holder, it is advantageous if a spacer is placed between two bits, the clear distance of which exceeds a specific value. The bits are then clamped to the spacer by the clamping device such that a type of sandwich clamping results. The high-precision adjustment of the clear distance between the bits is thus effected by the choice of thickness of the spacer. If the clear distance between two bits is to be increased, the use of another spacer or alternatively several spacers is necessary.
In a particularly preferred version, the holding elements are provided for the support or bearing of the bit essentially at three locations. The bit is firstly inserted into the holding element such that it touches the holding element at the three locations. Through the three locations, the position of the bit is precisely specified relative to die holding element. The fixing or clamping device then fixes bit in precisely this position. It is understood that the three locations need not actually be in the form of points, but as a rule represent precisely worked surfaces, preferably on the edge surfaces. The holding element then supports or bears the cutting-off insert essentially at three surfaces.
For some applications, it may be advantageous that each holding element has an attachment apparatus for the fixing of a bit in or at the holding element. Such an attachment apparatus can also be a screw connection. In particular when greater numbers of workpieces are to be produced, before for example the clear distance between the bits must be varied or the clear distance between the bits does not require a high degree of precision, the fixing of each individual bit at the holding element can be advantageous.
It is obvious that not every bit available on the market can be used in the cutting-bit holder according to the invention. A particularly suitable cutting bit has a main part as well as at least one cutting part having a cutting edge, the at least one cutting part having an essentially constant width. It is understood that a cutting part which for example has chamfers only in the area of the cutting edge in order to optionally achieve a more favourable distribution of the cutting forces, also has an essentially constant width. The cutting bits according to the invention described here can also advantageously be used in other cutting-bit holders.
A cutting bit with a square basic shape and four cutting edges is particularly preferred.
In a preferred version, the cutting bit has two side surfaces or also main surfaces as well as several edge surfaces or rim faces, the cutting edges being arranged at the edge surfaces. In addition, the cutting bit preferably has an indentation or recess on at least one side face. A holding clement is then particularly preferred which has a holding seat matched to the recess of the cutting bit. The cutting bit with its recess can thereby be placed on the holding seat of the holding element, so that this, exact position of the bit relative to the holding element results xe2x80x9cautomaticallyxe2x80x9d. Many types of recess can be realized, thus for example the edge surfaces of the bit can be curved concavely at the recesses. It is understood however that the edge surfaces need not necessarily be concavely curved, but for example can also be constructed essentially developed in a V-shape.
A particular version of the bit provides for at least two recesses. In this case, the holding element has a bit seat with not only a suitably shaped surface, but also two salients which are matched to the recesses of the bit. Thus it is possible to insert the bit even more precisely into the holding element, as holding element and bit now engage at two surfaces, matched to each other.
Particularly preferably, the main part of the bit has a greater width than the at least one cutting part. Through the variation of the width of the main part, the clear distance between two adjacent cutting bits can be varied without using a spacer, without changing the width of the cutting part (and thus the width of the groove to be cut). It is understood that the cutting part need not necessarily sit centrally on the main part. Rather the cutting part could also be arranged on the main part such that at one side of the bit, the surface of the main part and the surface of the cutting part lie on one level, whilst, on the other side of the bit, the surface of the cutting part and the surface of the main part lie on parallel levels such that a step is formed where the main part transforms into the cutting part.
The bit preferably has a cutting edge with a top face and a clearance face, the top face and clearance face forming an angle a which is less than 90xc2x0.
Particularly preferably, the cutting edge has a chamfer. In addition, a concavely curved section which favors chip forming and chip flow can be provided at the end of the top face.
Particularly preferably, the bit is developed such that it is orientated in the position when inserted into the cutting-bit holder such that a positive cutting rake or adjustment angle results during the cut-off process.
In a particularly preferred version, a safety apparatus is provided which secures a bit or a turning bit and/or a spacer in the tool seat, the safety apparatus having an elastic element which is arranged such that a turning tool or a spacer can be inserted into the tool seat and/or removed from this seat only upon exertion of a force on the elastic element. This ensures that the bit holder is capable of frictionally holding a bit or a turning bit and/or a spacer in the tool seat such that, although an axial positioning or adjustment of the turning bit or of the spacer is easily possible, an unintended falling-out or slipping-out of the turning bit and/or of the spacer from the tool seat of the cutting-bit holder is prevented. The cutting bit and/or the spacer is therefore inserted into the tool seat of the cutting-bit holder accompanied by exertion of a force. Depending on the version of the cutting bit or of the turning tool, in the position when inserted, either the elastic element can now exert a force on the turning tool or the spacer, so that this cannot fall out of the tool seat essentially because of the increased frictional force, or the safety apparatus can engage or lock in a positioning notch of the cutting bit or of the spacer, so that the cutting bit or the spacer can be released from the tool seat and then removed only upon exertion of a force on the elastic element. It is understood that such a safety apparatus according to the invention can be used to advantage with all cutting-bit holders with at least one tool seat for a turning bit or a spacer.
A version in which the elastic element has a spring is particularly preferred. The safety apparatus preferably has a sleeve in which the elastic element is arranged.
A particularly expedient version of the safety apparatus provides that a contact element is present which is provided for engagement with a turning bit or with a spacer when this is inserted into the tool seat. The contact element can, in choice of material and in configuration easily be matched to the material and shape of the turning bit or of the spacer or optionally of the positioning notch. Upon insertion of the turning bit or the spacer into the tool seat, the turning tool or the spacer comes into contact with the contact element. The contact element which is connected to the elastic element is then forced out of its idle position, against the spring force of the elastic element.
The contact element is preferably arranged on the side of the elastic element facing the tool seat inside the sleeve. It is then expedient if the sleeve tapers at the end facing the tool seat at least to the extent that the contact element cannot fully emerge from the sleeve at the end of the latter that faces the tool seat. In other words, the sleeve has at its one end a stop such that the contact element is pressed against the stop by the elastic element when neither turning tool nor spacer is inserted in the bit seat. Upon insertion of the turning bit or the spacer, the contact element is then pressed against the spring force slightly into the sleeve and away from the stop. When inserted, the elastic element then exerts a force on the turning bit or the spacer via the contact element, so that this cannot fall out of the tool seat.
Advantageously, the contact element can be rotated or swivelled about at least one axis. This easily allows a longitudinal adjustment of the bit whilst simultaneously a safeguard against the falling-out of the turning bit or the spacer from the cutting-bit holder or the holding element is ensured. The contact element can for example be a ball which is pressed by the force of the spring against the turning bit or the spacer and can be rotated about its own axis within the sleeve.
For some applications, it may be advantageous if an adjustment apparatus is provided with which the force which must be exerted on the elastic element during the insertion and/or during the removal of the turning bit and/or the space into or from the tool seat, can be set. It is thereby possible to set up a holding force of the safety apparatus matched to the application.
In the case of a particularly preferred cutting-bit holder, several safety apparatuses are provided. Advantageously, a safety apparatus is allotted to each turning bit to be housed and/or each spacer to be housed. This ensures that each individual spacer or each individual turning bit can be held securely in the cutting-bit holder or in the holding element.
As already mentioned, it is possible to hold the turning bit or the spacer in the cutting-bit holder solely due to the force exerted by the elastic element on the spacer or the turning tool via the contact element.
However a version in which the spacer and/or the bit has a positioning notch which is provided for engagement with a safety apparatus is particularly preferred. Upon insertion of the turning bit or the spacer into the tool seat of the cutting-bit holder, the contact element is pressed against the elastic element, so that this is compressed. In the process, the contact element engages with the external surface of the turning bit or of the spacer, At the moment when the spacer or the turning bit has assumed its correct seat in the cutting-bit holder, the contact element reaches the positioning notch of the spacer or of the turning bit, so that the elastic element can at least partially relax again and the contact element engages in the positioning notch. In other words, the contact element locks into the positioning notch. If the turning bit or the spacer is now to be removed again from tool seat of the cutting-bit holder, the elastic element must be compressed again so that the contact element can emerge from the positioning notch of the spacer or of the turning bit.
The turning bit comprises, according to the invention, a main part as well as at least one cutting part which has a cutting edge, the also having a positioning notch which is provided for engagement with a safety apparatus in the position when inserted into the bit holder.
The positioning notch is advantageously arranged essentially in the area of a recess of a side surface.
Particularly preferred a version of the bit which has several, preferably four, cutting edges, a positioning notch being allotted to each cutting edge. This facilitates a secure a holding of the cutting bit in the cutting-bit holder in every envisaged orientation of the cutting bit.
In a particularly preferred version of the cutting bit, the recesses are developed essentially in a V-shape, a positioning notch being arranged in only one V-leg. This arrangement of the positioning notch has the advantage that an unintentional incorrect insertion of the cutting bit into the bit seat is prevented, as there is then no positioning notch at the corresponding point at which the contact element of the safety apparatus is located. Consequently, given suitable development of the bit, the bit is held securely in the bit seat only when the cutting bit is arranged such that the cutting edge is arranged in the correct orientation.